Reward functions 4-6 share a common operation of computing an exponential function of the calculated metric to obtain the reward as used in ([1]}, [2]})
\(r(d_m)=\exp \left(-\frac{1}{2 \sigma _{w}^{2}}(d_m + d_o)\right),\) 
where \(\sigma _w\)  is a configurable width, \(d_o\)  is a distance offset and \(d_m\)  is the input metric.
